Preparation of filaments



Aug. 19, 1947. E, BLUDWORTH ETAL 2,425,782

PREPARATION OF FILAMENTS Filed March 4, 1944 .IHHIII.

I N VEN TORS W R 0 W D U L B E H P E s O J N O 5 T U H D L E F N A C 0 wMA iatented Aug. 19 1947 UNITED STATES PATENT OFFICE PREPARATION OFFILAMENTS Joseph E. Bludworth and Canfield Hutson, Cumberland, Md.,assignors to Celanese Corpora tion of America, a corporation of DelawareApplication March 4, 1944, Serial No. 525,036

Claims.

This invention relates to the production of artificial filaments byspinning operations, and relates more particularly to the preparation bywet-spinning processes of artificial filaments having a basis of anorganic derivative of cellulose, such as cellulose acetate, or otherfilamentforming material, from solutions of said filamentformingmaterials in a volatile solvent.

Artificial filaments or threads having a basis of an organic derivativeof cellulose, such as cellulose acetate, or other filament-formingmaterial, are usually prepared by extruding a solution of celluloseacetate in acetone under pressure through a jet on spinneret into anatmosphere of warm or hot air or other evaporative medium circulatingthrough a spinning cabinet. The filaments become solidified onevaporation of the volatile solvent and are then associated to form athread which is wound into a package form by suitable winding means.Such dry spinning operations require a substantial capital outlay sincethe cabinets are of a height of feet or more and large volumes of airmust be heated and passed through the cabinets by means of blowers tocarry oiT the voltaile solvent Vapors. Then, too, the Valuable solventmust be recovered from the air by means of an expensive solvent recoverysystem. To avoid these disadvantages, it has been proposed to preparesuch artificial filaments by wet-spinning methods wherein a solution ofcellulose acetate in acetone or other solvent is extruded through a jetor spinneret into an aqueous coagulating bath. Various coagulating bathshave been suggested with a View toward producing strong and elasticfilaments. Among the various coagulating baths which have been mentionedare aqueous baths containing thiocyanates and aqueous baths containingvarious organic compounds which are solvents or latent solvents for thefilament-forming cellulose acetate material. These coagulating bathsyield artificial filaments having somewhat improved properties overthose obtained by extrusion into a water bath free of inorganic salts ororganic solvents. However, it has not been possible, heretofore, by theusual wet-spinning operations, to form said filaments at spinning speedsgreater than 66 to 100 meters per minute, which speeds do not approachthe usual commercial spinning speeds achieved by. dry-spinning, and,consequently wet-spinning is comparatively uneconomical.

It is, therefore, an important object of this invention to provide animproved process for the production of artificial filaments having abasis 2 of an organic derivative of cellulose, such as celluloseacetate, or other filament-forming material by wet-spinning processes,whereby filaments of improved tenacity and elongation characteristicsmay be obtained.

Another object of this invention is the production of artificialfilaments by wet-spinning processes at speeds substantially higher thanthose which have heretofore been practical on a commercial scale.

Other objects of this invention will appear hereinafter from thefollowing detailed description and the accompanying drawing.

In the drawing:

Fig. 1 is a perspective View of our novel spinning apparatus for theproduction of artificial filaments by wet-spinning methods.

Fig. 2 is a perspective view of another embodiment of our novel spinningapparatus, and

Fig. 3 is a perspective view of another embodiment of our novel spinningapparatus.

Like reference numerals indicate like parts throughout the views of thedrawing;

In accordance with our invention, the production of artificial filamentshaving a basis of cellulose acetate, or other filament-forming material,of improved tenacity and elongation characteristics may be achieved byextruding a solution of said filament-forming material in a volatilesolvent through a jet or spinners-t into an enclosed chamber filled witha fog or mist, comprising droplets of a liquid in which the volatilesolvent employed is soluble but in which the filament-forming materialis insoluble, and then, after solidification oi the filaments in thechamber passing the solidified filaments into a bath of the liquidplaced outside of the chamber. The volatile solvent evaporated from thefilaments in the fog-filled chamber is absorbed by the fog or mist andthe solvent remaining in the solidified filaments after they leave thechamber is Washed out in the liquid bath. After leaving the liquid bath,the filaments are dried in warm air, or other suitable, drying media.The filaments may then be collected in package form. The filamentsobtained by our novel wet-spinning process are of substantiallyincreased tenacity compared with filaments heretofore produced bywet-spinning operations and possess excellent elasticitycharacteristics. Furthermore, the filaments may be produced at spinningspeeds of 300 meters per minute, and more. The filaments are ofcommercial quality. Optimum results are obtained with a solution ofcellulose acetate in acetone by employing a fog or mist of Waterdroplets in the 3 spinning chamber and then passing the solidifiedfilaments through a water bath or solution prior to forming the yarnpackage.

Preferably, the solution of cellulose acetate in the acetone is heatedprior to extrusion. Suitable heating means may be provided and thetemperature at which is it extruded may be from 80 F. to 206 F. Thetemperature of the water bath may be any temperature above the freezingpoint of water and may vary from temperatures as low as 33 F. up to 170F. or more, but preferably the temperature is maintained at lower thanthe usual room temperatures. The water sprayed and atomized in or intothe cabinet to form the fog or mist of water droplets through which thefilaments pass may be any temperature above the freezing point of wateror even be preheated, but preferably the temperature is from about 33 F.to 60 F. so that the temperatures of 40 F. to 60 F. are maintained inthe cabinet.

In order further to illustrate our invention, reference may be had tothe accompanying drawing.

Referring now to the drawing and more particularly to Fig. 1, referencenumeral 3 indicates an enclosed cabinet of cylindrical or other shapeprovided at 3 and 5 with suitable spraying or atomizing nozzles adaptedto form a finely divided fog or mist when water is forced through saidnozzles under pressure. At the top of cabinet 3 is tube 6 connected to acandle filter l which carries at the lower end thereof a spinning nozzleor jet 8 through which the spinning solution is continuously extrudedunder pressure to form filaments 9. To heat the spinning solution prioto extrusion, candle filter l is surrounded by a heating jacket IE]adapted to receive a circulating fluid heating medium H, such as steam,hot water, heated oil or the like. The fluid medium II enters jacket lthrough a pipe l2 and is discharged through a pipe is.

Filaments 9 traverse a vertical path through the fog or mist in cabinet3 and leave through a suitable opening id at the base of the cabinet 3.They are then taken up by a rotating feed roller l5, rotating in thedirection shown, which is partly submerged in a trough l8 containingwater or other non-solvent liquid. After making several revolutionsabout rotating feed roller l5, filaments 9 pass around an auxiliaryrotating feed roller or thread guide ll, again around roller l and thenthrough a suitable guide it to be taken up in any suitable manner toform a yarn package Hi. The feed roller [5, when rotating and partiallysubmerged in trough l6, agitates and imparts motion to the water. Thedepth and quantity of water which adheres or clings to the outsidecircumferential surface of the revolving roller 15, is proportional tothe speed of rotation. At higher speeds water tends to be flung from thewetted surface of the roller [5 by centrifugal force. In order toregulate the quantity of water retained on the roller surface and thethrow-off, there is provided an adjustable dcctor blade, deflector orwiper l5-a, with a suitable facing of felt, rubber or other material.The volatile solvent which is evaporated from filaments 9 is dissolvedby the water mist or fog which condenses in cabinet 3 and drips intotrough E6. The solvent remaining in the filaments 9 is washed out duringthe passage of the filaments through the water bath. Suitable means (notshown) are provided for circulating the water in trough 95 whereby thesolvent-laden water is continuously or intermittently removed andreplaced with fresh water free of solvent. The liquid removed fromtrough I6 is then sent to a suitable solvent recovery system where theorganic solvent is separated from the water, concentrated and thenemployed again to form a spinning solution. Suitable yarn finishes mayalso be added to the water bath, if desired.

In the embodiment of our invention shown in Fig. 2, the filaments 9 areextruded into the cabinet 3 through jet 3 and, after traversing throughthe fog or mist of Water droplets, the filaments are passed directlyinto the water bath or solution contained in trough iii. The runningfilaments 9 pass under guides 20 and 2| which are submerged beneath theliquid, then over guide 22 and around driven feed roller 23. Thefilaments leaving roller 23 are passed to suitable winding means (notshown) are then taken up to form a suitable yarn package if). In thismodification of our invention, a somewhat increased path through theliquid bath in trough i6 is provided and the feed roller is outside ofthe bath instead of being submerged therein. In lieu of directing thefilaments in a vertical path through cabinet 3, they may, of course, becaused to traverse a substantially horizontal or semihorizontal path, asshown in Fig. 3, by suitably positioning cabinet 3, or they may enterinto the aqueous medium at any other desired angle. Entering thefilaments into the water bath at an angle allows for a more extendedpath through the liquid bath.

While our invention has been more particularly described in connectionwith the production of filaments having a basis of cellulose acetatefrom solutions thereof in acetone, it is to be understood, of course,that the filament-forming material employed may be any other organicderivative of cellulose or any other suitable filament-forming material.Suitable organic derivatives of cellulose are, for example, celluloseesters, such as cellulose propionate or cellulose butyrate, mixed esterssuch as cellulose acetate-butyrate or cellulose acetate-propionate, orcellulose ethers, such as ethyl cellulose or benzyl cellulose. Othermaterials from which filaments may be formed by extrusion of saidfilament-forming material in a volatile solvent may also be employed inthe preparation of artificial filaments by our novel wet-spinningprocess. As suitable volatile solvents which may be employed in lieu ofacetone there may be mentioned ethyl etheralcohol, di-chlor-methane,carbon disulfide, etc., while suitable liquids in which the volatilesolvents are soluble but in which the filament-forming material isinsoluble and which may be employed to form the mist and the liquid bathare methanol, hexane, etc.

It is to be understood that the foregoing detailed description is givenmerely by way of illustration and that many variations may be madetherein without departing from the spirit of our invention.

Having described our invention, what we desire to secure by LettersPatent is:

1. Process for the production of artificial filaments having a basis ofa filament-forming material by wet-spinning processes, which comprisesextruding a solution of a filament-forming material in a volatilesolvent into a setting atmosphere consisting essentially of a mist ofdroplets of a liquid in which said volatile solvent is soluble andsaidfilament-forming material is insoluble, wherein saidextrudedmaterial is solidified, and

passing said solidified materials through a bath of said liquid.

2. Process for the production of artificial filaments having a basis ofa filament-iorming material by wet-spinning processes, which comprisesextruding a solution of a filament-forming organic derivative ofcellulose mate-rial in a volatile solvent into a setting atmosphereconsisting essentially of a mist of droplets of a liquid in which saidvolatile solvent is soluble and said filamentforming material isinsoluble, wherein said extruded material is solidified, and passingsaid solidified materials through a bath of said liquid.

3. Process for the production of artificial filaments having a basis ofa filament-forming material by wet-spinning processes, which comprisesextruding a solution of a filament-forming cellulose acetate material ina volatile solvent into a setting atmosphere consisting essentially of amist of droplets of a liquid in which said volatile solvent is solubleand said filament-forming material is insoluble, wherein said extrudedmaterial is solidified, and passing said solidified materials through abath of said liquid.

4. Process for the production of artificial filaments having a basis ofa filament-forming material by wet-spinning processes, which comprisesextruding a heated solution of a filament-forming material in a volatilesolvent into a setting atmos phere consisting essentially of a mist ofdroplets of a liquid in which said volatile solvent is soluble and saidfilament-forming material is insoluble, wherein said extruded materialis solidified, and passing said solidified materials through a bath ofsaid liquid.

5. Process for the production of artificial filaments having a basis ofa filament-forming ma.- terial by wet-spinning processes, whichcomprises extruding a heated solution of a filament-forming organicderivative of cellulose material in a volatile solvent into a settingatmosphere consisting essentially of a mist of droplets of a liquid inwhich said volatile solvent is soluble and said filament-formingmaterial is insoluble, wherein said extruded material is solidified, andpassing said solidified materials through a bath of said liquid.

6. Process for the production of artificial filaments having a basis ofa filament-forming ma terial by wet-spinning processes, which comprisesextruding a heated solution of a filament-forming cellulose acetatematerial in a volatile solvent into a setting atmosphere consistingessentially of a mist of droplets of a liquid in which said volatilesolvent is soluble and said filament-forming material is insoluble,wherein said extruded material is solidified, and passing saidsolidified materials through a bath of said liquid.

7. Process for the production of artificial filaments having a basis ofa filament-forming material Iby Wet-spinning processes, which comprisesextruding a solution of cellulose acetate in acetone into a settingatmosphere consisting essentially of a mist of water droplets whereinsaid extruded cellulose acetate material is solidified, and passing thesolidified cellulose acetate material through water.

8. Process for the production of artificial filaments having a basis ofa filament-forming material by Wet-spinning processes, which comprisesextruding a heated solution of cellulose acetate in acetone into asetting atmosphere consisting essentially of a mist of water dropletswherein said extruded cellulose acetate material is solidified andpassing the solidified cellulose acetate material through water.

9. Process for the production of artificial filaments having a basis ofa filament-forming material by wet-spinning processes, which comprisesextruding a solution of cellulose acetate in acetone heated to atemperature of F. to 206 F. into a setting atmosphere consistingessentially of a mist of water droplets wherein said extruded celluloseacetate material is solidified, and passing the solidified celluloseacetate material through water.

10. Process for the production of artificial filaments having a basis ofa filament-forming material by wet-spinning processes, which comprisesextruding a solution of cellulose acetate in acetone heated to atemperature of 80 F. to 206? F. into a setting atmosphere consistingessentially of a mist of Water droplets wherein said extruded celluloseacetate material is solidified, and passing the solidified celluloseacetate material through water at a temperature of 33 F. to F.

JOSEPH E. BLUDWORTH. CANFIELD l-IUTSON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,838,121 Vles Dec. 29, 19312,032,606 Whitehead Mar. 3, 1936 2,054,852 Dreyfus Sept. 22, 19362,081,171 Dreyfus May 25, 1937 2,186,135 Childs Jan. 9, 1940 888,260Planchon May 19, 1908 2,252,684 Babcock Aug. 19, 1941 1,979,403Ostermann Nov. 6, 1934 2,161,354 Imray June 6, 1939 FOREIGN PATENTSNumber Country Date 251,680 Great Britain Apr. 30, 1926 289,233 GreatBritain Apr. 26, 1928 368,230 Great Britain Aug. 26, 1930 645,696Germany June 2, 1937 175,296 Germany Sept. 7, 1906

